Compared with uncaffeinated women, those who drank the equivalent of four or more cups of coffee a day are more likely to drink alcohol and smoke cigarettes and less likely to volunteer their time in church or community groups. But a new study finds that well-caffeinated women have a key health advantage over their more abstemious sisters: they’re less likely to become depressed.

In the back-and-forth world of research on caffeine’s effects, the latest study suggests that women who get several jolts of java a day may do more than get a quick boost: their mental health may see sustained improvement even as the physical stresses of aging accumulate. Among a large population of women tracked for as long as 18 years each, the women who routinely consumed the highest levels of caffeine were 20% less likely than those who drank little to none to become depressed when they were nearing or in their 60s.

Coffee, which ounce-for-ounce delivers the strongest dose of caffeine, was most women’s pick-me-up of choice. And generally, the more caffeine a woman drank, the more likely she was to be in good mental health. The study was published Monday in the Archives of Internal Medicine.

“A small amount of coffee may keep you more active and more happy, and that may result in the long run in better brain health,” said Dr. Alberto Ascherio, the senior author of the study. Cautioning that his group’s findings are preliminary, Ascherio added that they should ease concerns among female coffee addicts as they enter midlife; the average age of the participants was 63 years in 1996, when researchers began tracking the incidence of depression among the women.

“There’s no reason, from what we know, for people to cut back on their coffee consumption, unless, of course, it makes them feel bad,” said Ascherio, professor of epidemiology and nutrition at Harvard University’s School of Public Health. Ascherio was the lead author of a 2003 study that linked high coffee consumption with lower rates of Parkinson’s disease in men, but not in women. That early study, however, did turn up one key warning for women: among heavy coffee drinkers who had taken hormone replacement therapy, the likelihood of developing Parkinson’s disease rose.

To gauge the link between caffeine consumption and depression, the authors of the latest research drew upon the long-running Nurse’s Health Study. Some 53,739 women who participated in that larger study completed periodic surveys of their eating habits for 14 years. While women with a prior history of depression were included in the study, none of those participating showed significant depressive symptoms, or had a depression diagnosis in 1996, when the researchers began to measure depression rates.

In an effort to gauge caffeine’s long-term, rather than its immediate effect, researchers waited two years after a woman’s last dietary report to begin inquiries about her mental health. At that time also, they asked about health and lifestyle behavior, such as alcohol consumption, tobacco use, exercise, marital status and involvement in social or community groups. Then, at least twice over the next four-year period, they would ask her whether she had been diagnosed with depression or had begun taking antidepressant medication on a regular basis in either of the previous two years.

In addition to their greater likelihood of smoking and drinking alcohol, regular coffee drinkers were less likely to be obese or have high blood pressure or cholesterol levels.

In an editorial comment also published in the Archives of Internal Medicine on Monday, Dr. Seth A. Berkowitz called the study the first large-scale study of coffee consumption to evaluate a mental health outcome in women, and as such “makes an important contribution.” Berkowitz is an internal medicine physician at UC San Diego Medical Center.

A number of studies have found, contrary to long-held belief, that coffee consumption may aid cardiovascular health and reduce strokes. The few other studies of coffee consumption and depression have focused largely on men, or on people who committed suicide. Those largely linked caffeine consumption with lower rates of depression and suicide. But since women are twice as likely to suffer depression as men (yet far less likely to take their own lives), the authors of the current study argued that understanding how caffeine affects women specifically is important.